The present disclosure relates to systems and methods for stabilizing bone structures. More particularly, it relates to systems and methods for forming a cavity inside a bone structure, such as a vertebral body, and delivering a stabilizing material into the cavity.
Surgical intervention at damaged or compromised bone sites has proven highly beneficial for patients, for example patients with back pain associated with vertebral damage.
Bones of the human skeletal system include mineralized tissue that can be generally categorized into two morphological groups: “cortical” bone and “cancellous” bone. Outer walls of all bones are composed of cortical bone, which has a dense, compact bone structure characterized by a microscopic porosity. Cancellous or “trabecular” bone forms the interior structure of bones. Cancellous bone is composed of a lattice of interconnected slender rods and plates known by the term “trabeculae”.
During certain bone-related procedures, cancellous bone is supplemented by an injection of a palliative (or curative) material employed to stabilize the trabeculae. For example, superior and inferior vertebrae in the spine can be beneficially stabilized by the injection of an appropriate, curable material (e.g., PMMA or other bone cement or curable material). In other procedures, percutaneous injection of stabilization material into vertebral compression fractures, by, for example, transpedicular or parapedicular approaches, has proven beneficial in relieving pain and stabilizing damaged bone sites. Such techniques are commonly referred to as vertebroplasty. Other skeletal bones (e.g., the femur) can be treated in a similar fashion. Regardless, bone in general, and cancellous bone in particular, can be strengthened and stabilized by palliative insertion or injection of bone-compatible material.
Using vertebroplasty as a non-limiting example, a conventional technique for delivering the bone stabilizing material entails placing an access cannula with an internal stylet into the targeted delivery site (i.e., the vertebral body). The access cannula and stylet are used in conjunction to pierce the cutaneous layers above the hard tissue to be supplemented, then to penetrate the hard cortical bone of the vertebra, and finally to traverse into the softer cancellous bone underlying the cortical bone. Once positioned in the cancellous bone, the stylet is removed, leaving the access cannula in an appropriate, lodged position for delivery of curable material (e.g., via a needle or tube inserted through the access cannula) to the trabecular space of the vertebral body that in turn reinforces and solidifies the target site.
In some instances, an effectiveness of the procedure can be enhanced by forming a cavity or void within the cancellous bone, and then depositing the curable material in the cavity. For example, a balloon or other expandable device can be initially deployed and then expanded. This action, in turn, compresses cancellous bone to form a cavity. To minimize the duration of the procedure and number of tools required, it is desirable to use the same access cannula to first guide delivery of the cavity forming device, and subsequently to guide delivery of the curable material. Stated otherwise, one desirable procedure entails initially locating and lodging a distal end of the access cannula within the bone, immediately adjacent the target site. The cavity forming device is then delivered through the access cannula to the target site and then operated to form the cavity. In this regard, the access cannula is normally a metal tube rigidly defining a central axis. Conventional cavity forming devices typically include a longitudinally linear shaft carrying the expandable body. With this linear configuration, the shaft/expandable body progress from the access cannula into the bone structure along a relatively straight or linear path that is coaxial with the access cannula's central axis. While viable, this linear approach may inhibit the surgeon's ability to form the cavity at a desired location. For example, with vertebroplasty, the confined nature of the inner vertebral body and surrounding anatomy oftentimes necessitates insertion of the access cannula immediately adjacent one of the vertebra's pedicles. This access site, in combination with the linear configuration of the access cannula and expandable body-carrying shaft, dictates that the expandable body can only be located in a relatively limited area in line with the access cannula's central axis. In some instances, this restricted spatial location of the expandable body relative to the desired target site may not be optimal.
In light of the above, a need exists for improved systems and methods for forming a cavity in a compromised bone site, such as a vertebral body, and for delivering stabilizing material to the so-formed cavity.